How setting an Object to null help Garbage Collection?

I was reading through some forums and found suggestion that setting an object to null helps Garbage collection? Is it true. How does it matter for GC whether a reference is already set to NULL or not, GS has to still do its check on the reference right??

You don't "set an Object to null". When you do var = null, what you are doing is "erasing", or removing, that reference to the Object. The Object itself still exists, but that reference to it no longer does. Once all references to an Object are removed, it will be Garbage Collected.